Lighting control systems automate the operation of lighting devices throughout a building or residence based upon preset time schedules and/or occupancy and/or daylight sensing. These systems may also be used to automate the operation of other electrical devices or appliances ranging from, for example, simple fans to more complex HVAC (heating, ventilating, and air conditioning) systems. These systems may further be used in conjunction with fire and/or security systems. Lighting control systems typically employ occupancy sensors and/or daylight sensors to determine which lighting devices to activate, deactivate, or adjust the light level of, and when to do so. Occupancy sensors typically sense the presence of one or more persons within a defined area and generate signals indicative of that presence. Daylight sensors typically sense the amount of daylight present within a defined area and generate signals indicative of that amount. Known lighting control systems receive those sensor signals at a central lighting control panel, which may be located, for example, in a building manager's control center. The control panel responds to the received signals by deciding which, if any, relays, switching devices, and/or dimming ballasts to drive in order to turn on or off and/or adjust the light levels of one or more lighting devices.
Lighting control systems are advantageous because they reduce energy costs by automatically lowering light levels or turning off devices and appliances when not needed, and they allow all devices in the system to be controlled from one location.
Known lighting control systems also have, however, many disadvantages. For example, one type of known system requires each sensor, manually-operated switch, and load (i.e., a lighting or other electrical device to be controlled by the system) to be hardwired to the lighting control panel or to a main communications bus, which is hardwired to the lighting control panel. Relays for connecting/disconnecting power to loads are usually incorporated in the control panel. Many commercial, educational, and industrial settings can have hundreds, if not thousands, of sensors, switches, and loads. Accordingly, hardwiring each device to a main bus or control panel often involves long wire runs that result in costly and time consuming installation and maintenance.
Another disadvantage of known lighting control systems is that all decision making occurs at the control panel. Thus, if the control panel becomes inoperative, all lighting devices in the system are no longer under automated control and some or all may not operate even manually. Similarly, if a connection to or from the control panel is severed, the lighting devices served by that connection are no longer under automated control and also may not operate manually.
Still another disadvantage is the one-way communication from the sensors to the control panel. Changes to a sensor's operational settings, parameters, or modes (e.g., sensor time delays, photocell set-points, etc.) have to be made at the individual sensor itself and cannot be made from the control panel.
Conversely, a further disadvantage is that any partial or system-wide functional change, such as an immediate need to override current system settings (e.g., during a fire or other emergency), cannot be made from anywhere but the control panel. Likewise, even routine modifications, such as to a preset time schedule of some or all of the lighting devices, cannot be made from anywhere but the control panel even if that location is not convenient at the time.
Another type of known lighting control system is referred to as a “DALI” (digital addressable lighting interface) system, which adheres to a standardized digital protocol. This system includes dimming and electrical ballasts as well as sensors (e.g., daylight and occupancy), manually-operated switches, lighting and perhaps other loads, and a central controller running application software. A DALI controller can communicate with devices in the system via bi-directional data exchange. However, a disadvantage is that every device in the system with which the controller is to communicate has to be assigned an address that has to be manually identified to the controller upon start-up (known as “commissioning”). Initial set-up and subsequent modification of a DALI-based system can thus be complicated and time consuming. Moreover, if the assignment of addresses does not correspond in some way to the devices' physical location, maintenance and replacement of faulty devices can also be complicated and time consuming. Another disadvantage of a DALI-based system is the limited number of addresses available, which is believed to be 64. DALI therefore cannot be used in large installations without using another technology to overcome the limitation, which increases the complexity of the system. DALI-based systems also have the same disadvantages as other known centrally-controlled systems: they are vulnerable to controller malfunctions/outages, severed connections, and the inability to make local or global operational mode changes from anywhere but the central controller.
In view of the foregoing, it would be desirable to be able to provide a networked, wireless lighting control system with distributed intelligence for both global and local lighting control capabilities and for local independent operation.